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I am in desperate need of help to improve the abysmal performance of my 802.11n wireless network. At best I get 30Mbs (this is an internet download) from a technology that boasts 300Mbs, even worse is the LAN where to date the best I have ever gotten is 1Mbs. It is literally quicker to copy the file to a USB drive and walk it to the other computer.

Infrastructure is this

  • AP 802.11n only broadcasting at both 2.4GHz and 5GHz
  • Mac with 802.11a/b/g/n card is connected to the AP via 5GHz
  • Linux with 802.11a/b/g/n card is connected to AP via 2.4GHz

I have conducted the following tests (results at end of post)

  • Internet based speed test wired and wireless
  • LAN file copy wired and wireless

I have read:

I have made the following optimizations

  • AP broadcasts only 802.11n on both 2.4GHz and 5GHz frequencies
  • 2.4GHz is on a channel with least interference (live in an apartment with lots of APs), this did make a 10Mb/sec improvement
  • Our AP is the only one transmitting on the 5GHz freq.
  • Security: WPA Personal WPA2 AES encryption
  • Bandwidth: 20MHz / 40MHz (I assume this to be channel bonding)

I have tried the following with 0 improvement

  • Dropped the Fragment Threshold to 512
  • Dropped the Request To Send (RTS) Threshold to 512 and 1
  • Even thought of buying a frequency spectrum analyzer, until I saw the cost of them!!!

Speed test results

Linux Wired:

Mac Wired:

Linux Wireless:

Mac Wireless:

LAN NFS 53,345,087 bytes (51MB) file

  • Linux Mac NFS Wired: 65.6959 Mb/sec
  • Linux Mac NFS Wireless: .9443 Mb/sec

All help is appreciated, even testing methods will be accepted.

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1  
None of those speeds seem to be concering. What makes you think your access point has the ability to provide faster speeds? Your wire and wireless upload speeds match, this means, your using 100% of the bandwidth and have very little packet loss. One has to remember that the 54 Mbit/s to 600 Mbit/s are the speeds you would see in a clean room. They are also an entirely different unit of measurement. –  Ramhound Sep 6 '13 at 11:30
    
How many Access Points can your computers see ? You will probably find that the Wifi provider is lying to you about speed (they ALL do it, its pretty much written in to the spec as you will never get anything close to the advertised speed in real life), and the amount of other devices "eating" into your available spectrum. You might be able to speed things up by changing WIFI channels, but if you can't you can always kill the power to your neighbours so their WIFI's stop interfering with yours :> –  davidgo Sep 7 '13 at 4:45

5 Answers 5

You say there are many other APs in your vicinity.

It is to be noted that if there are other wireless networks on the same channels as yours -

Your N router will set its speed at A, B or G speeds, depending on the speed of those other router/wireless networks.

Try selecting a channel that is only N or make the appropriate changes on those other routers to free channels for the N standard.

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What is serving the NFS data? Is this on the wired network?

See http://www.tp-link.us/article/?faqid=190 for finding the MTU fragmentation limits. If you can set the MTU on whatever is serving your NFS then you might be able to improve the wi-fi performance.

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If your wireless router is set to both 20/40MHz auto selection for Channel Bandwidth and there are a number of other Access Points in the area it may be having trouble using enough channels to actually support the 40MHz option.

When using the 20MHz option only one channel is used in the transmission of data, and makes it very obvious if you use any channel scanning utility on a computer or phone that it is overlapping with other Access Points in close proximity.

When attempting to work at 40MHz the router is actually extending from the base channel either up or down (normally this can be configured).

I followed advice for some time to simply using 20MHz channel bandwidth exclusively, but later was able to once again use the 20/40Mhz auto setting by being extremely particular about my control channel choice and the direction of channel extension.

I used the following application on my Android phone to check the impact of other Access Points on the channels I attempted to use:

Wifi Analyzer (Google Play)

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I recently resolved issues (dropouts, slow speed, etc) with my 802.11n wireless network by switching to one of the newer 'beamforming' routers. Since switching, everything is stable and fast now. :) I was previously using a good quality Linksys router, but it couldn't handle the interference from multiple nearby devices and walls, etc.

Switching to a beamforming router might be worth a try if nothing else works.

Cheers

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For the Internet, I have to agree with RAMHound that those speeds are about normal. Wireless has a lot more overhead so actual transfer rates are much lower than the spec. One thought though is the wireless speeds look about right for the original (draft) 150 Mbit 802.11 N. If you only upgraded the router/AP to 300N then you probably have the 150N cards in the computers or they are set to single channel mode (see http://compnetworking.about.com/od/wireless/f/80211n-300-mbps.htm).

For the LAN NFS, the difference here is much greater. Based on the Internet tests, on WiFi you should have about 12 Mbits. If you only tested that once or twice, it could have been a temporary issue otherwise the NFS may need optimizing for WiFi. This might help: http://ubuntuforums.org/archive/index.php/t-1047907.html

For testing the LAN easily, I use LAN Speed Test which has a Mac version available:

http://www.totusoft.com/downloads.html

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